Well drilling fluid material and process of preparing the same



Jan. 15, 1946. D. H. LARSEN 2,393,174 WELL DRILLING FLUID MATERIALS AND PROCESSES OF PREPARING THE SAME Filed Aug. 12, 1942 n WA TER-f Patented Jan. 15, 1946 WELL DRILLING FLUID MATERIAL AND PRQCEASSVOF PREPARING THE SAME Delmar H. Larsen, Los Angeles, Calif., assignor to National lLead Company, Los Angeles, Calif., a corporation of New Jersey Application August 12, 1942, Serial, No. 454,627

8 Claims.

water-absorption and swelling.

In the drilling of wells, particularly oil and gas wells, a drilling fluid or mud is employed,

whose function it is to carry the cuttings and to wall the bore hole. Among the materials which have been found particularly suitable are emulsoid colloids such as a' concentrated colloidal clay, viz., an alkali-metal gel-forming bentonite, described in the Harth Patent No. 1,991,637. Such a bentonite is of the reversible type, i. e., when hydrated it forms a gel but which can be dehydrated without destruction of the gel-forming properties.

In drilling muds, important single property is that of great lter-cake impermeability, or, as is more commonly thought of, a low water loss when the mud is filtered. While the viscosity characteristic or gelling power of an ineilicient bentonite can be increased by caustic addition agents, these may disadvantageously affect its water-loss characteristics. Thus, the viscosity of a bentonite suspension can be sharply raised by the addition of such materials as magnesium oxide or Portland cement; but while such additions greatly increase the gelling power of the bentonite, they simultaneously affect the ltercake permeability most adversely, giving rise to a high water loss.

In some cases it is diiiicult to secure an emcient gel with a reversible bentonite, and this may be due to any one or both of the following causes,

, namely; that either the bentonite `or the water,

or both, is or are deiicient in water-soluble electrolytes. Such is the case with some of the California bentonites, and is also the case where the water contains only from 1 to 4 grains per gallon (17-68 parts per million) of the watersoluble electrolytes.

One of the objects of this invention is to provide a well drilling fluid material, whichfiwill have a good gel-forming characteristic at a low water-loss. Another object is to provide a process oftreating such a material to secure such result.-

Another object is to provide a process of preparing a drilling fluid to secure such a result.

Further objects will appear from the detailed description in which will4 be set forth a number of embodiments: it is to be understood, however, that this invention is not limited to such embodiments. y

In the accompanying drawing,

Figure l shows the eiect of certain alkalimetal salts on the water loss and viscosity of suspensions of a typical California bentonite5 such as can be beneiiciated by the process embodying this invention.

vFigure 2 shows the salutary effects of certain alkali-earth salts on the suspensions of the same bentonite.

Figure 3 shows the effects of both alkali-metal salts and alkali-earth salts on a. suspension of a Wyoming bentonite which already contains sufficient electrolyte so that it does not have to be beneciated by the process embodying this invention.

Generallystated, and in accordance with the illustrative embodiments of this invention, the objects are attained as follows: Where the bentonite is deficient in water-soluble electrolytes, there is added thereto or combined therewith a non-caustic electrolyte of a character and in an amount sufllcient only to make up such deficiency and to substantially promote gelling thereof but without material increase of water-loss when an aqueous drilling uid embodying such treated bentonite is made up and used. Where the water is deficient in such an electrolyte, the procedure is to add to the water employed for hydrating the bentonite, suilicient of the electrolyte to make up such deficiency and to substantially promote the gelling of the bentonite without material increase of water-loss. In general, where the summation of the total electrolyte content of both the bentonite and water is decient, the procedure is to add sulcient of the electrolyte to secure the desired result.

The electrolyte, which may be employed, may be a salt, such as a mnovalent salt, although some divalent salts can be used. Salts which are particularly useful, because economical, as well as effective, are sodium bicarbonate .and sodium chloride; however, the potassium and ammonium salts may be employed. Other salts noted on the drawing are: sodium sulphate, magnesium sulphate, barium chloride, calcium chloride and potassium chloride. Any of these salts may be mixed with the ground bentonite and supplied, as such, for hydration. Where the water is deiicient in the electrolyte the procedure is to add the salt to the water. The electrolyte may, however, be added to the bentonite` high gelling power in distilled water with a low water loss. The specic resistivity of such a suspension'at 15 centipoises (Stormer at 600 R.. P. M.) is 620 ohm-centimeters. The specific 'resistivity of a similar suspension of a typical Callfornia bentonite such as would be beneilciated by the process of this invention is about 1112 ohm-centimeters. Generally, therefore, a standard can be adopted as a V2% suspension of 500 ohm-centimeters resistivity, above which the bentonite or the water in which itis hydrated may be said to be deficient in water-soluble electrolytes. If, therefore, 5V2% of a given bentonite (such as California bentonite) and a given water, when mixed together, given greater resistivity than BOO'ohm-centimeteisfthen add sfumcient of the electrolyte to reduce the resistivity to 560 ohm-centimeters. V

' The drawingA shows the effect 'of various electrolytes on bentonite suspensions in distilled water and a designation, such as .02N NaCl indicates that the solution is a 3&00 normal solution. In all of these the percentage of bentonite was fil/2% with Water to make a total of 100%. In Figures 1 and 2 for California bentonite, the

water'was distilled water, as it was also in Figure 3 where the bentonite ,was Wyoming bentonite. In Figures 1 and 2 the resistivity of the suspension was 1112 ohm-centimeters. The abscissa and ordinates indicate the data shown.

The viscosity was obtained -by'a Stormer instrunient at 600 R. P. M. at 79 The Awater loss was determined in accordance with the method of the American Petroleum Institute. Of course, the higher the water loss, as determined by this method, the greater is the filter-cake permeability, and accordinglythe less desirable is the drilling fluid or mud for drilling.-

Figure 1 shows the striking eiect of even small percentages ofelectrolyte on a California benl tonite suspension in distilled water. yThe addition of the various electrolytes increase the'viscosity characteristics or gelling power very rapidly withoutan-y material increase in water, loss, provided, of course, that the amounts ofl elec- --trqlytes did not exceed the maxima noted on the drawing. This is even true of sodium bicarbonate', .while even potassium chloride is practical. Figure 2 also shows that the alkaline earth salts vwere eiiective in California bentonite. .Af reference to `Figure 3 will show that the effects of various electrolytes onWyoming bentonites in suspension in distilled water result in no improvement; in fact, in all cases .except forsodium chloride, at a very small percentage, the eii'ect' was harmfull inthat the waterloss was ,increased rather than decreased. This is due to the fact that, as noted above, Wyoming bentonite 1 has a high gelling power, even in distilled water with low water loss. 'I'he specific resistivity of the Wyoming bentonite suspension employed here was 620,'ohm-centimeters in distilled water and wasreduced to only 404 ohm centimeters by adding V100 normal solution of sodium chloride. 'On the other hand, in Figure 1 the same amount of sodium chloride increased the viscosity by' more A than'seven times without materially affecting the water loss and reduced the resistivity to 575 ohm centimeters.

7 `It will, therforebe seen that the invention accomplishes its objects. While it does not necesg' 4sarily enable a bentonite deicient in electrolyte tobe better, in both gelling power and water loss, than an electrolyte-rich' bentonite, it does enable a bentonite deficient in electrolyte to be. at least,

equal to a bentonite not decient in electrolyte,

in its characteristic of eiiicient viscosity or -gelling power at a low water loss.

5 susceptible of various embodiments within the scope of the appended claims without departing from the spirit of this invention.

Having thus described the invention, what is claimed is: f

- l'. A well-drilling iiuid material, comprising, a Areversible concentrated colloidal clay, viz., an alkali-metal gel-forming bentonite which itself is deficient in water-soluble electrolytes and containing an added non-caustic electrolyte of a character and in an amount sufficiently only to make up such deficiency and to substantially promote gelling of the bentonite but without material increase of water-loss.

2. A well-drilling fluid material,comprising, a

lreversible Yalkali-metal bentonite which itself isA decient in water-soluble electrolytes and containing an added non-caustic'electrolyte of a character and in' an amount sumcient only to make up such deciency and to-substantialwepromote gelling of the bentonite butvwithout material increase of water-loss.

3. A well-drilling fluid material, comprising, a reversible alkali-metal bentonite which itself is deficient in water-soluble electrolytes butwhich contains a. small percentage of 'an added noncaustic water-soluble salt of a character and sufcient only to make up such deiiciency and to substantially Ipromote gelling of the bentonite without material increase of water-loss.

' ing, adding to a reversible alkali-metal bentonite which itself is deiicient in water-soluble electrolytes, a non-caustic electrolyte of a character and in an amount suillcient only to make up 4o such deficiency and -to substantially promote gelling of the bentonite.

5. The process of treating bentonite, compris- Ang, adding to a reversible alkali-metal bentonite deficient in water-soluble electrolytes, a noncaustic electrolyte of ai character and in an amount suillcient only to make up such deficiency and to substantially promote gelling of the bentonite without material increase of water-loss.

6. The process of treating bentonite, compris- 5o ing, adding to a reversible alkali-metal bentonite which is deficient in" water-soluble electrolytes, a small percentage of a non-caustic water-soluble salt, viz., sufcient only 'to overcome such deficiency and to substantially promote gelling of the bentonite without material increase of water- '1. The process of preparing a drilling fluid of water and of a reversible concentrated colloidal clay, viz., an alkali-metal bentonite, comprising, Aadding to a water deficient in water-soluble electrolytes, an electrolyte of a character and in an amount sufcient only to overcome such deiiciency` and to substantially promote gelling of the bentonite Without material increase of water- 4. The process of treating bentonite, compris- 

